The invention relates to an electronic ignition system for gasoline internal combustion engines with a Hall sensor for generating the reference signal corresponding to the position of the crankshaft or the pistons in the cylinders wherein the ignition point is electronically controlled in dependence upon the speed and the load.
Electronically controlled ignition systems for gasoline internal combustion engines have been advantageously employed in automotive vehicles for some years. These ignition systems control the ignition coil current in such a way that the latter does not reach its maximum until shortly before the ignition point. In the known systems, the ignition coil current is furthermore limited to a defined maximum value. To identify the position of the motor crankshaft either a Hall or an induction sensor is used. These known ignition systems do not control the ignition point electronically in dependence upon the speed and the load, but rather effect this desired control with the aid of mechanical systems. For example, the speed dependency of the ignition point is achieved by the mechanical adjustment of the ignition distributor with the aid of a centrifugal force system, and the load dependency similarly by a mechanically operating vacuum system.
Furthermore, electronic ignition systems wherein the ignition point is electronically controlled in dependence upon speed and load have recently become known. To this end, the engine-related data are transferred to an electronic data store. These data are processed in a microprocessor according to a predetermined program to provide output data which control the ignition procedure. The store and the microprocessors preferably consist of MOS modules. The output stage amplifier and the control of the primary coil current in the ignition coil are, on the other hand, still realized by bipolar technology. The reason for this is that high demands are made on the ignition system with respect to current and voltage stability. The ignition system should, furthermore, operate temperature independently within a large temperature range.
These relatively new ignition systems, often referred to as "characteristic curve ignition" have the advantage that the formerly commonly used mechanical adjustment devices are replaced by electronic components. The disadvantage of characteristic curve ignition is that the electronic modules of the ignition themselves are comparatively expensive and complicated, with the result that characteristic curve ignition has hitherto only been installed in automobiles of the higher price range.
Substantial cost could be saved with an electronic ignition system without mechanical systems, without store and microprocessor, wherein the speed- and load-dependent ignition point is controlled by an analog bipolar system. This is promoted by U.S. Pat. No. 4,324,216. With this ignition system, the information for control of the ignition point is derived from the signal of an induction sensor whose amplitude and curvature are speed-dependent. The disadvantage of this ignition system is that the ignition point in the idle range changes between two states and the speed-dependent ignition point only depends on the curvature of the induction sensor. The ignition point can, therefore, not be influenced in an engine-related manner in the electronic system.
Furthermore, the unavoidable dispersion of the induction sensors fully affects the speed dependency of the ignition point. There is no load-dependent electronic control of the ignition point in this ignition system.